Effects of lamb age, muscle type, and 24-hour activity of endogenous proteinases on postmortem proteolysis1

Abstract

The objectives of this study were to examine the amount of postmortem proteolysis in three different lamb muscles at different ages and to determine whether a relationship exists between the extent of myofibrillar degradation and certain endogenous proteinase activities. Wether lambs were slaughtered at 8 (n = 6) and 26 (n = 6) wk of age. Samples were taken from the longissimus (LM), gluteus medius (GM), and supraspinatus (SS) muscles for determining myofibrillar fragmentation index (MFI) at 1 and 7 d postmortem, cathepsins B and B + L, cystatin(s), mu- and m-calpain and calpastatin 24-h activities, and muscle fiber type and area. Muscle samples were removed for SDS-PAGE analysis at 0, 1, and 7 d postmortem. The SS muscle consisted of more (P less than .05) oxidative fibers, whereas no age effects (P greater than .10) were observed for fiber type. The younger lambs had higher (P less than .01) cathepsins B and B + L, cystatin, and calpastatin 24-h activities but less (P less than .01) m-calpain activity than did the 26-wk-old lambs. Within each age, the SS muscle had the highest (P less than .05) mu-calpain, m-calpain, and calpastatin specific activities. The MFI values and SDS-PAGE results indicate that less proteolysis occurred in the SS muscle. Samples from 26-wk-old lambs tended to have greater MFI values at 1 and 7 d postmortem, especially for the LM and GM muscles. From these results, it seems that less postmortem proteolysis occurs in younger and more oxidative muscles and this may be attributed to the greater calpastatin 24-h activity.

The effect of maternal nutrient restriction during late gestation on muscle, bone and meat parameters in five month old lambs

“…Moreover, values for muscle fibre area presented in this study are similar to previous results from cross breed wethers age 182 days (Whipple and Koohmaraie, 1992), Dorset wethers, age 159-177 days and crossbreed market lambs . In a recent study in lambs, the authors reported that nutrient restriction during early gestation seemed to affect hyperplasia of the muscle cells, whilst a restriction later in gestation resulted in lighter muscles, in keeping with lighter birth weights cf.…”

Identification of small troponin T peptides generated in dry-cured ham

“…In this way, Whipple and Koohmaraie (1992) examined the amount of post-mortem proteolysis in three different lamb muscles and concluded that degradation products derived from TnT in supraspinatus, a slow type muscle, were distinct from those in longissimus and gluteus medius, fast type muscles. On the other hand, Muroya, Nakajima, and Chikuni (2003), established that slow-oxidative muscles were richer in slow TnT isoforms than were the fast muscles.…”

Progeny of high muscling sires have reduced muscle response to adrenaline in sheep

“…Studies in maturing sheep report an increase muscle fibre area in both glycolytic and oxidative muscle fibres (Whipple and Koohmaraie, 1992). Brandstetter et al (1998) found young growing bulls expressed proportionally more slow type 1 myofibres as they matured.…”